1. Field of the Invention
The present invention is related to a method and apparatus for sterilizing or disinfecting containers. More specifically, the present invention relates to a method and apparatus for sterilizing containers at relatively low temperatures.
2. Description of the Related Art
Sterilization of food and medicinal packaging is necessary to kill microorganisms that may be present on the packaging. The failure to properly sterilize food packaging could lead to contamination of the food within the packaging, which could lead to sickness and sometimes death to a consumer of the food. The food industry has developed various methods to sterilize food packaging to create aseptic packaging.
Traditional aseptic packaging is typically sterilized using hydrogen peroxide. As set forth in Title 37 of the Code of Federal Regulations (“CFR”), Section 178.1005, the U.S. Food and Drug Administration (“FDA”) has determined that a hydrogen peroxide solution containing not more than 35% hydrogen peroxide may be safely used to sterilize polymeric food-contact surfaces. Sterilization using hydrogen peroxide typically requires high temperatures or ultraviolet light to generate hydroxyl radicals from the hydrogen peroxide, which in turn inactivate the microorganisms on the packaging material. The temperature needed to generate free radicals from the hydrogen peroxide is usually in excess of 65° C. and is frequently in the range of 120-135° C.
Most food packaging is composed of a polymer material such as plastic bottles. The FDA has provided a list of polymer materials that may be utilized with hydrogen peroxide. The list, set forth in 37 CFR 178.1005(e), includes ethylene-acrylic acid copolymers, ethylene-carbon monoxide copolymers, ethylene-methyl acrylate copolymer resins, ethylene-vinyl acetate copolymers, ionomeric resins, isobutylene polymers, olefin polymers, polycarbonate resins, polyethylene terephthalate (“PET”), poly-1-butene resins and butane/ethylene copolymers, polystyrene and rubber modified polystyrene polymers and vinylidene chloride/methyl acrylate copolymers. Sterilization of plastic bottles is difficult at elevated temperatures since the bottles become quite fluid and deform during the sterilization process. In addition, an extended drying process is required to evaporate the residue of peroxide (35%) which boils at 108° C. Further, some plastic materials like PET bind or absorb peroxide making it very difficult to achieve the residue limit of 0.5 parts per million (“ppm”) for food packaging required by the FDA as set forth in 37 CFR 178.1005(d).
One method of sterilization is disclosed in Sizer et al., U.S. Pat. No. 5,326,542 for a Method And Apparatus For Sterilizing Cartons, which discloses using ultraviolet light to sterilize food cartons.
Another method is disclosed in Sizer et al., U.S. Pat. No. 5,770,232 for a Method Of Disinfecting The Food Contact Surfaces Of Food Packaging Machines And Disinfecting Solution Therefor, which discloses using a solution of 0.1% to about 1% by weight of hydrogen peroxide and from about 0.001% to about 0.1% by weight of sodium acid pyrophosphate applied at a temperature of about 70° C. for at least fifteen minutes.
Another method is disclosed in Frisk, U.S. Pat. No. 5,928,607 for a Bottle Sterilization Method And Apparatus, which discloses using ultraviolet radiation from an excimer lamp to generate ozone from oxygen to sterilize plastic bottles.
Another method is disclosed in Lentsch et al., New Zealand Patent Number 282691 for a Method For Sanitizing And Destaining Food Ware And Utensils Using A Composition Comprising Peroxycarboxylic Acid, Carboxylic Acid, Peroxide And A Carrier, discloses a sanitizing concentrate composition of 1-20 weight % peroxycarboxylic acid, 10-50 weight % carboxylic acid, 3-35 weight % hydrogen peroxide and the balance a carrier.
Yet another method is disclosed in Wang, European Patent Number 0411970 for Sterilization Of Containers By Means Of Hydrogen Peroxide, Peracids, And U.V. Radiation, which discloses using between 15 to 25% concentration of hydrogen peroxide and peracetic acid at a temperature of 20-30° C. with U.V. light at a wavelength of less than 300 nanometers for 8-12 seconds to effectuate a greater than 6.0 log reduction in the number of B. subtilis spores.
Yet another method is disclosed in Smith et al., U.S. Pat. No. 6,479,454 for Antimicrobial Compositions And Method Containing Hydrogen Peroxide And Octyl Amine Oxide, which discloses using a composition of an amine oxide hydrogen peroxide to sanitize food contact surfaces.
Another method is disclosed in Taggart, U.S. Pat. No. 6,209,591 for an Apparatus And Method For Providing Container Filling In An Aseptic Processing Apparatus, which discloses spraying atomized hydrogen peroxide onto bottles within a sterilization chamber that has sterile air present at a temperature of 135° C .
Another method is disclosed in Taggart, U.S. Pat. No. 6,536,188 for a Method And Apparatus For Aseptic Packaging, which discloses spraying hot hydrogen peroxide onto bottles, allowing approximately 24 seconds for activation and removal of the hydrogen peroxide, and then filling the bottle with a low acid beverage.
Hall, II et al., U.S. Pat. No. 5,344,652 for a Anticorrosive Microbicide discloses a two part component containing a first part of hydrogen peroxide, peracetic acid and acetic acid, and a second part of VICTAWET®, which is a sodium hydroxide reaction product of an aliphatic alcohol (2-ethyl hexyl) and phosphorous pentoxide. The VICTAWET® reduces the corrosiveness of the peroxide/peracetic biocide.
Nystrom et al., U.S. Pat. No. 5,900,111 for a Process For Sanitizing Post-Consumer Paper Fibers Using Heat And Hydrogen Peroxide discloses sanitizing waste paper hydrogen peroxide and using sodium hydroxide to adjust the pH of a fiber stream during the sanitizing process.
Japanese Patent Publication Number 02-154763 for a Method For Removing Hydrogen Peroxide discloses removing excess hydrogen peroxide from soft contact lenses subjected to a hydrogen peroxide sterilization treatment by using a removing agent essentially consisting of sodium thiosulfate, sodium pyruvate, peroxidase and a metallic catalyst, with the soft contact lenses also subjected to ultrasonic waves.
Japanese Patent Publication Number 07-291236 for a Method Of Sterilizing Food Container discloses using hot water with a germicide forced into an interior of a food container, with the germicide being hydrogen peroxide, peracetic acid, mixture of hydrogen peroxide and peracetic acid or sodium hypochlorite.
Although the prior art has disclosed many different methods for sterilizing containers, especially food containers, there is still a need for using hydrogen peroxide at low temperatures in an expedited manner in order to reduce costs, increase container filling productivity and most importantly adequately sterilize the containers.